Bharat Sanchar Nigam Limited Telecom Technical Assistant last year papers

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1. In a D.C. generator, if the brushes are given a small amount of forward shift, the effect of armature is

a. Totally demagnetizing

b. Totally magnetizing

c. Partly demagnetizing and partly cross magnetizing

d. Totally cross magnetizing

2. The air gap between stator and armature of an electric motor is kept as small as possible

a. To get a stronger magnetic field

b. to improve the air circulation

c. To reach the higher speed of rotation

d. To make the rotation easier.

3. Two series motors are coupled. One motor runs as generator and other as motor. The friction losses of the two machines will be equal when

a. Both operates at same voltage

b. Both have same back emf

c. Both have same speed

d. both have same excitation

4. Plugging of D.C. motor is normally executed by

a. Reversing the field polarity

b. Reversing the armature polarity

c. Reversing both the armature and field polarity

d. Connecting a resistance across the armature.

5. Transformer oil transformer provides

a. Insulation and cooling

b. B. Cooling and lubrication

c. Lubrication and insulation

d. Insulation, cooling and lubrication

6. Leakage fluxes of transformer may be minimized by

a. Reducing the magnetizing current to the minimum

b. Reducing the reluctance of the iron core to the minimum

c. Reducing the number of primary and secondary turn to the minimum

d. Sectionalizing and interleaving the primary and secondary windings

7. Electric power is transformed upon one coil to other coil in a transformer

a. Electrically

b. Electro Magnetically

c. Magnetically

d. Physically

8. The most suitable and economical connection for small high voltage transformer is-

a. Star- Delta connection

b. Delta- Delta connection

c. Delta- Star connection

d. Star- Star connection

9. An alternator is said to be over excited when it is operating at

a. Unity power factor

b. Leading power factor

c. Lagging power factor

d. Either lagging or leading power factor

10. In an A.C. machine, the armature winding is kept stationary while the field winding is kept rotating for the following rason

a. Armature handles very large currents and high voltages

b. Armature friction involving deep slots to accommodate large coils is easy if armature is kept stationary

c. Ease of cooling the stator than rotor

d. None of the above.

11. In a synchronous motor, the torque angle is the

a. Angle between the rotating stator flux and rotor poles

b. Angle between the magnetizing current and back emf

c. Angle between the supply voltage and back emf

d. None of the above

12. A 3-phase synchronous motor is said to be “floating” when it operates

a. On no load and without loss

b. On constantly varying load

c. On pulsating load

d. On high load and variable supply voltage

13. Speed of synchronous motor depends upon

a. Number of poles

b. Supply frequency

c. Both (a) and (b)

d. Neither (a) nor (b)

14. Imbalance in the shaft of an induction motor occurs due to

a. Slip rings

b. Overheating of winding

c. Non uniform of air gap

d. Rigid consturcion

15. Squirrel cage induction motor has

a. Zero starting torque

b. Very small starting torque

c. Medium starting torque

d. Very high starting torque

16. The principle of operation of a 3-phase induction motor is similar to that of a

a. Synchronous motor

b. Repulsion – start induction motor

c. Transformer with a shorted secondary

d. Capacitor – start, induction – run motor

17. The speed/load characteristics of a universal motor are similar to those

a. D.C. shunt motor

b. D.C. series motor

c. A.C. motor

d. None of the above

18. Single phase A.C. motor generally used for vacuum cleaners is

a. Universal motor

b. Repulsion motor

c. Hysteresis motor

d. Reluctance motor

19. Buchholz relay is used for the protection of

a. Switch yard

b. Transformers

c. Alternators

d. Transmission lines

20. The type of braking used in traction system is

a. Mechanical braking

b. Electro – pneumatic braking

c. Vacuum braking system

d. All the above

21. The function of processing zenger diode in a UJT circuit used for triggering of SCRs is to

a. Expedite the generation of triggering pulses

b. Delay the generation of triggering pulses

c. Provide a constant voltage to UJT to prevent erratic firing

d. Provide a variable voltage to UJT as the source voltage changes

22. The frequency of a ripple in the output voltage of a 3 – phase semi converter depends upon

a. Firing angle and load resistance

b. Firing angle and supply frequency

c. Firing angle and load inductance

d. Only on load circuit parameters

23. The SCR is turned off when the anode currents falls below

a. Forward current rating

b. Break – over voltage

c. Holding current

d. Latching

24. V4 characteristics of emitter of a UJT is

a. Similar to CE with linear and saturation region

b. Similar to FET with a linear and pinch of region

c. Similar to tunnel diode in some respects

d. Linear between the peak point and valley point

25. A transformer works on

a. DC

b. AC

c. AC & DC both

d. Neither AC not DC

26. Which of the following device is used in transformer?

a. Tube light

b. Electric heater

c. Mobile phone

d. Rectifier module

27. Earth electrodes can be in the form of

a. rods or piper

b. stripes

c. plates

d. any of above

28. Carbone or metal brushes are used in

a. DC generators only

b. AC generators only

c. Both AC & DC generation

d. None of above

29. Energy is lost due to Joule’s heating effects in winding of transformer. This is called

a. Copper loss

b. Eddy current loss

c. Flux loss

d. None

30. In refrigeration cycle heat is lost in

a. Cooling coil

b. Condenser

c. Compressor

d. Expansion valve

31. The power factor of AC circuit is

a. R/X

b. R/Z

c. Z/R

d. Zero

32. Silicon controlled output is good if ripple factor is

a. Switch

b. Transformer

c. Amplifier

d. None of above

33. The rectifier output is good if ripple factor is

a. More

b. Less

c. Constant

d. None of above

34. Protective relays can monitor large AC current by means of

a. Current transformer

b. Potential transformer

c. Micro transformer

d. None of above

35. The combines AM of two similar batteries connected in parallel is:

a. halved

b. doubled

c. remain constant

d. none of above

36. The current in circuit having 5 V EMI source and 10 Ohm resistance is:

a. 2 Amp

b. 50 Amp

c. 5 Amp

d. ½ Amp

37. The chopper is a device to change

a. Voltage

b. Current

c. Frequency

d. None of these

38. The power consumption, in case of centrifugal loads (like pump, fan, blower etc) is proportional to:

a. speed

b. square of speed

c. cube of speed

d. none of these

39. Which of these need to be measured after rewinding the motor:

a. no load current

b. air gap

c. winding resistance

d. all of the above

40. Five percent increase in supply frequency will change the synchronous speed of motor by:

a. -5%

b. +5%

c. -10%

d. +10%

41. Which of the following is the best inverter?

a. square wave inverter

b. sine wave inverter

c. pure sine wave inverter

d. triangular wave inverter

42. For driving a motor in a tape recorder or record player, the motor used is generally:

a. a synchronous motor

b. a hydraulic motor

c. an induction motor

d. a dc series motor

43. The DC motor starter used with a constant speed shunt motor is:

a. 2 point starter

b. 3 point starter

c. 4 point starter

d. 5 point starter

44. A commutator in a DC motor converts

a. AC to DC

b. DC to AC

c. Both AC to DC and DC to AC

d. None of these

45. Two transformers running in parallel will share the load according to their:

a. leakage reactance

b. pu impedance

c. efficiency

d. rating

46. The size of the Earth Wire is determined by:

a. the ampere capacity of the service wires

b. the atmospheric conditions

c. the voltage of service wires

d. none of these

47. The function of lightning arrester is:

a. to limit the short circuit fault current

b. to provide path to high voltage surge to earth

c. to reduce arcing

d. none of these

48. Surge protector provide:

a. high impedance to normal voltage

b. low impedance to surge

c. both (a) and (b)

d. none of these

49. Earthing is necessary to give protection against

a. voltage fluctuation

b. overloading

c. danger of electric shock

d. high temperature of conductors

50. The primary function of fuse is to

a. protect the appliance

b. open the circuit

c. prevent excessive current

d. protect the line

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Here I am providing the list of few questions of Bharat Sanchar Nigam Limited Telecom Technical Assistant exam question paper which you are looking for .
Bharat Sanchar Nigam Limited Telecom Technical Assistant exam question paper
1. Pick up wrong statement
(a) A group of interconnected individual components known as circuit elements is called a network.
(b) A humped network is an arrangement of physically separate resistors, inductors and capacitors.
(c) Distributed network is one, which the resistive, inductive and capacitive effects are inseparable for network analyses.
(d) A branch is a network having four elements.

2. Kirchoff’s laws for networks are:
(a) The algebraic sum of branch currents meeting at any node is zero.
(b) The algebric sum of voltage drops in any set of branches forming a closed circuit or loop must be equal to zero.
(c) Both (a) and (b)
(d) Neither (a) and (b)

3. Mutually coupled circuit is a circuit which is:
(a) Bilateral
(b) Unilateral
(c) None of these
(d) Either (a) or (b)

4. Duality is a
(a) Transformation in which current and voltages are interchanged
(b) Active sources become passive sources
(c) Passive sources become active sources
(d) Both (b) and (c)

5. Combined inductance of two inductors L1 and L2 connected and voltages are interchanged
(a) L1 + L2
(b) (L1 + L2)/ L1
(c) (L1 + L2) / (L1 X L2)
(d) (L1 X L2) / (L1 + L2)

6. Normal analysis techniques are based on
(a) Thevenin’s theorem
(b) Tellegan’s theorem
(c) Superposition theorem
(d) Kirchoff’s Law

7. Two voltage sources can be connected in parallel when they are equal in
(a) Magnitude
(b) Frequency
(c) Phase
(d) All the above

8. The kirchoff’s law fail in
(a) Linear circuits
(b) Non-linear circuits
(c) Lumped parameter circuits
(d) Distributed parameter circuits

9. Which of the following is a nonreciprocal network ?
(a) A network consisting of all resistances
(b) A network consisting of all capacitances
(c) A network consisting of all inductances
(d) A transistor model

10. When two systems obey equations of the same form the systems are said to be
(a) Similar system
(b) Identical system
(c) Analogous system
(d) Digital system

11. For a highly selective circuit
(a) It must have large value of Q
(b) It must have high value of capacitance to produce resonance at fixed frequency
(c) Either (a) or (b)
(d) Neither (a) nor (b)

12. A network consisting of four terminals is called a
(a) One port network
(b) Two port network
(c) Four port network
(d) None of the above

13. Driving point of a network is
(a) A port where voltage or current source is connected
(b) A terminal where load is connected
(c) A port where load is connected
(d) None of the above

14. Ceramic filters are similar in construction to
(a) Crystal filters
(b) Crystal ladder filters
(c) Crystal lattice
(d) Mechanical filters

15. When two port networks are connected in parallel the resultant
(a) Z parameters are the some of individual parameters
(b) Y- parameters are the some of individual parameters
(c) Both (a) and (b)
(d) Neither (a) nor (b)

16. Electric wave filters
(a) Allow electric signals with specified frequency range
(b) Suppress signals outside a specified range
(c) Both (a) and (b) occurs simultaneously
(d) Either (a) or (b) occur at a time

17. A cascade connection of low pass filter and high pass filter is called
(a) Band pass filter
(b) Band elimination filter
(c) Neither (a) nor (b)
(d) Both (a) and (b)

18. The response of a network is decided by the location of
(a) Its poles
(b) Its zeros
(c) Either (a) nor (b)
(d) Both (a) and (b)

19. Example of two port network is
(a) Transformer
(b) Transmission line
(c) Bridge circuit and transistor circuit
(d) All of the above

20. The circuit whose properties are same in either direction is called
(a) Universal circuit
(b) Reversible circuit
(c) Unilateral circuit
(d) Bilateral circuit

21. Distortion in transmission line is due to
(a) Delay distortion
(b) Phase distortion
(c) Frequency distortion
(d) All the above

22. The general parameters distributed along a transmission line are
(a) R&L only
(b) L&C only
(c) C&G only
(d) R, L, C&G

23. Phase distortion is prominently caused by
(a) circuit transients
(b) non linear characteristics
(c) linearity
(d) none

24. The voltage or current from the receiving end towards the sending end, decreasing in amplitude with increasing distance from the load is called
(a) incident wave
(b) medium wave
(c) reflected wave
(d) none of above

25. E.M. Waves of UHF is propagated efficiently via
(a) parallel wire transmission lines
(b) open wire transmission lines
(c) wave guides
(d) coaxial cables

26. Norton theorem is valid for network containing only
(a) linear elements
(b) no linear elements
(c) resistance
(d) reactance

27. The maximum power is absorbed by one network from other, joined to it at two terminals when the impedance of one is
(a) complex conjugate of other
(b) square root of other
(c) same as other
(d) none of above

28. The decrease in effective conductor cross section at high frequencies
(a) decrease the conductor resistance
(b) increase the conductor resistance
(c) no change in conductor resistance
(d) none of above

29. Voltage standing wave ratio lies in the range
(a) 0 to 1
(b) 1 to infinity
(c) 0 to infinity
(d) -1 to +1

30. Attenuators have applications
(a) in AC circuits only
(b) in DC circuits only
(c) in AC as well DC circuits
(d) in low frequency circuits only

31. In an network
(a) the number of tree branches is equal to the number of links
(b) the number of tree branches cannot be equal to the number of links
(c) the number of tree branches has no relation with the number of links branches
(d) none of these

32. In open line transmission systems, attenuation is more at
(a) lower frequencies
(b) medium frequencies
(c) higher frequencies
(d) remains constant

33. a power ratio 100 is equivalent to
(a) 10 dB
(b) 20 dB
(c) 50 dB
(d) 100 dB

34. The velocity factor for small widely spaced conductors such as open wire line in air is very nearly
(a) 0.66
(b) 0.98
(c) 0.82
(d) 0.76

35. Transmission of power to a load over a transmission line achieves optimum value when standing wave ratio (SWR) becomes
(a) 2 : 1
(b) 1 : 2
(c) 1 : 1
(d) 1 : 10

36. The VSWR in a short circuited loss less transmission line equals
(a) infinity
(b) unity
(c) zero
(d) none of above

37. The velocity factor of a transmission line
(a) is always greater than unity
(b) depend upon the permittivity of the surrounding medium
(c) is lease for air medium
(d) is governed by skin effect

38. Which of the following is not correct
(a) voltage source is an active element
(b) current source is a passive element
(c) resistance is a passive element
(d) conductance is a passive element

39. A network is said to be nonlinear if it does not satisfy
(a) superposition condition
(b) homogeneity condition
(c) both superposition and homogeneity conditions
(d) associative condition

40. An capacitor with zero initial condition at t = 0+ act as a
(a) short circuit
(b) open circuit
(c) current source
(d) voltage source

41. An inductor stores energy in
(a) electrostatic field
(b) electromagnetic field
(c) magnetic field
(d) core

42. In series LCR circuits, at resonance,
(a) current is maximum, power factor is zero
(b) current is maximum, power factor is unity
(c) current is minimum, power factor is unity
(d) none of above

43. In an RCL series circuit, during resonance, the impedance will be
(a) zero
(b) minimum
(c) maximum
(d) none of above

44. When a source is delivering maximum power to load, the efficiency of the circuit is always
(a) 50%
(b) 75%
(c) 100%
(d) None of above

45. In a linear network, when the ac input is doubled, the ac output becomes
(a) two times
(b) four times
(c) half
(d) one forth

46. A passive network has
(a) current sources but no voltage sources
(b) voltage sources but no current sources
(c) both current and voltage sources
(d) no voltage or current sources

47. Two resistances are connected in parallel and each dissipates 50 waits. The total power supplied by the source is
(a) 25 watts
(b) 50 watts
(c) 100 watts
(d) 200 watts

48. Three bulbs of 60 watts each are connected is parallel across 220v, 50 Hz supply. If one bulb burns out
(a) only remaining two will operate
(b) remaining two will not operate
(c) all of three will operate
(d) there will be heavy current from the supply

49. The amplitude of an audio signal is 10 and that of carrier wave is 50. Percentage modulation is:
(a) 0.2
(b) 20
(c) 5
(d) 60

50. The main advantage of PCM system is:
(a) lower bandwidth
(b) lower power
(c) lower noise